Stent device delivery systems are known in the art. The purpose of such a system is to deliver a stent device to a diseased vascular lumen. The stent device provides a support structure against collapse of the diseased vascular lumen. There are at least two types of stent device delivery systems that are of relevance to the present invention.
A first type provides a rolling outer sheath for deploying a stent device. Such a “rolling” outer sheath system is disclosed, for example, in U.S. Pat. No. 6,544,278, which is incorporated by reference in its entirety into this application. The outer sheath is made from a tubular sleeve that is folded back upon itself in order to define an inner layer, an outer layer and a fold-over portion connecting the inner layer and the outer layer. The inner layer and the outer layer overlay the stent device in a delivery configuration of the stent device. The outer layer is axially movable relative to the inner layer in a proximal direction, which causes the fold-over portion to move axially from a distal end to a proximal end of the stent device in a rolling manner, thereby retracting the outer sheath from the stent device. The stent device, unconstrained by the outer sheath, is able to radially expand into an operative configuration for supporting the diseased vascular lumen.
A second type of prior art delivery system provides an outer sheath that slides, rather than rolls, over the stent device in retracting the outer sheath from the stent device. Such a delivery system is disclosed in, for example WO 2006/133959, which is incorporated by reference in its entirety into this application. In this “pullback” outer sheath system, a proximal end of the outer sheath is pulled upon in order to drag the outer sheath axially from the stent device.
In terms of deployment force, rolling outer sheath delivery systems are advantageous in some circumstances as compared to pullback outer sheath delivery systems. In pullback outer sheath delivery systems, friction between the outer surface of the stent device and the inner surface of the outer sheath has to be overcome in order to move the outer sheath relative to the stent device. The longer the stent device, the greater the friction that has to be overcome. This puts certain constraints on what materials can be used for the outer sheath because of strength issues. Rollback outer sheath delivery systems are not as constrained by high frictional force considerations, but deployment force can still be a problem as, during rollback, the fold-over portion must generally slide against a more proximal portion of the inner layer. However, two-layer rollback constructions can disadvantageously increase the cross-sectional profile of the stent relative to single-layer pullback construction. In order to allow for a rolling outer sheath delivery system of comparable profile to a pullback system, the outer sheath is made of thinner, and thus weaker, materials than an equivalent pullback outer sheath delivery system. However, if the friction during rollback exceeds the strength of the materials used, reliability of the rolling outer sheath stent delivery system may be jeopardized.
In both the pullback outer sheath delivery stent device delivery systems and the rolling outer sheath stent device delivery systems, a pull member is used to apply a pulling force to retract the outer sheath from the stent device. The pull member may extend from a handle portion to a position just proximal of the stent device where it is attached to the outer sheath. One way to attach a pull member to an outer sheath is disclosed in WO 2006/133959, which is referred to above. In this document, outer and inner bands are arranged with the outer sheath compressed between them. A pull wire or pull member is brazed to the inner band and runs all the way back to a handle portion of the stent device delivery system. A strong and reliable connection between the pull member and the outer sheath is essential for successful deployment of the stent device by retracting the outer sheath. It is desirable to provide an alternative manner of strongly attaching the pull member to the outer sheath, while also retaining a low profile configuration.
Accordingly, in one embodiment, provided is a stent device delivery system that is reliable in terms of deployment of the stent device by retracting the outer sheath and is low profile for ease of delivery of the stent device to the diseased vascular lumen site. In one embodiment, provided is a method of making such a stent device delivery system. Other advantages of features of the present invention will become apparent to the skilled reader from the following description of embodiments of the invention.